What should we do about the nvme atomics mess?

[Nilay Shroff]

On 10/20/25 7:12 PM, John Garry wrote:
> On 10/07/2025 06:07, Nilay Shroff wrote:
>>> Considering multi-controller subsystems, some controllers might have
>>> namespaces with only 512b formats attached, and other controllers might
>>> have some 4k mixed in, so then they can't all consistently report the
>>> desired AWUPF value. They'd have to just scale AWUPF based on the
>>> largest sector size supported. Which I guess is what the current wording
>>> is guiding toward, but that just suggests host drivers disregard the
>>> value and use NAWUPF instead. So still option III.
>> Yes, I agree — option III seems to be the best possible way forward.
>> However, does this mean we would disregard atomic write support for any
>> multi-controller NVMe vendor that consistently reports a valid AWUPF value
>> across all controllers and namespace formats, but sets NAWUPF to zero?
> 
> Hi Nilay,
> 
> Does the drive which you are using report NAWUPF as zero (as hinted)?
> 
> If so, have you tried the following https://lore.kernel.org/linux-nvme/20250820150220.1923826-1-john.g.garry@oracle.com/
> 
> We were considering changing the NVMe driver to not use AWUPF at all...

Yes, I just tested your patch with the latest upstream kernel on my drive, 
which reports a non-zero AWUPF but a zero NAWUPF.

And your opt-in change works well on my disk. So we may consider 
merging this change if everyone agrees.

Thanks,
--Nilay